Theringed seal (Pusa hispida) is a smallearless seal species found inArctic andsub-Arctic regions. Its common name is derived from a distinctive patterning of dark spots surrounded by light gray rings.
Recently, the biggest threat to ringed seals has been thechanging temperature in the Arctic and the detrimental changes to sea ice that follow. Declines insnowpack andsea ice due to increasing ocean temperatures and atmospheric temperatures poses a threat to their survival. However, some projections indicate that the extinction of their predators due to warming may ultimately allow ringed seal numbers to thrive.[4]
The ringed seal is the smallest and most common seal in the Arctic, with a small head, short cat-like snout, and a plump body. Its coat is dark with silver rings on the back and sides and a silver belly, giving this seal itsvernacular name.[5] Depending on subspecies and condition, adult size can range from 100 to 175 cm (39.5 to 69 in) and adult weight can vary from 32 to 140 kg (71 to 309 lb).[6] Its average length is about 5 ft (1.5 m) long, with an average weight of about 50–70 kg (110–150 lb).[3] Though it is generally considered the smallest species in the true seal family, several related species, especially theBaikal seal, may approach similarly small dimensions. Their small front flippers have claws more than 2.5 cm (1 in) thick that are used to maintain breathing holes through ice sheets as thick as 6 ft (1.8 m).[3]
Ringed seals occur throughout theArctic Ocean. They can be found in theBaltic Sea, theBering Sea and theHudson Bay. They prefer to rest onice floe and will move farther north for denser ice. Twosubspecies,P. h. saimensis andladogensis, can be found in freshwater.
Ringed seals have a circumpolar distribution from approximately 35°N to the North Pole, occurring in all seas of the Arctic Ocean. In the North Pacific, they are found in the southern Bering Sea and range as far south as the seas of Okhotsk and Japan. Throughout their range, ringed seals have an affinity for ice-covered waters and are well adapted to occupying seasonal and permanent ice. They tend to prefer large floes (i.e., > 48 m in diameter) and are often found in the interior ice pack where the sea ice coverage is greater than 90%. They remain in contact with ice most of the year and pup on the ice in late winter-early spring.[13]
Ringed seals are found throughout the Beaufort, Chukchi, and Bering Seas, as far south as Bristol Bay in years of extensive ice coverage. During late April through June, ringed seals are distributed throughout their range from the southern ice edge northward. Preliminary results from recent surveys conducted in the Chukchi Sea in May–June 1999 and 2000 indicate that ringed seal density is higher in nearshore fast and pack ice, and lower in offshore pack ice. Results of surveys conducted by Frost and Lowry (1999) indicate that, in the Alaskan Beaufort Sea, the density of ringed seals in May–June is higher to the east than to the west of Flaxman Island. The overall winter distribution is probably similar, and it is believed there is a net movement of seals northward with the ice edge in late spring and summer. Thus, ringed seals occupying the Bering and southern Chukchi seas in winter apparently are migratory, but details of their movements are unknown.[13]
Ringed seals reside in arctic waters and are commonly associated with ice floes and pack ice.[3] The ringed seal maintains a breathing hole in the ice thus allowing it to use ice habitat that other seals cannot.
Females reach sexual maturity at 4 years old while males do not reach maturity until 7 years old.[3] During the spring breeding season, females construct lairs within the thick ice and give birth in these structures. Females give birth to a single pup on ice floes or shorefast ice in March or April after a 9-month gestation period. Pups are weaned after two months[3] and build up a thick layer ofblubber.
Females usually begin mating in late April.[3] Males will roam the ice for a mate. When found, the male and female may spend several days together before mating, after which the male looks for another mate.
Ringed seals live about 25 to 30 years.[3] They are solitary animals and when hauled out on ice, they separate themselves from each other by hundreds of yards.[3]
Preparation of the ringed sealSkin of the ringed seal.
Ringed seals have long been an important component of the diet of Arcticindigenous peoples throughout their range, and continue to be harvested annually by many communities.[3]Early Paleoeskimo sites inArcticCanada revealed signs of harvested ringed seals dating from c. 4000–3500BP, likely captured in frozen cracks and leads in the ice, with a selection for juveniles and young adults.[17]
In 2012 the Government ofNunavut warned pregnant women to avoid eating ringed sealliver due to elevated levels ofmercury, although they stressed eating traditional "country food" is still healthy for adults.[18]
Bycatch in fishing gear, such as commercial trawls, is a threat to ringed seals. Climate change is potentially the most serious threat to ringed seal populations since much of their habitat is dependent upon pack ice.[3]
The estimated population size for the Alaska stock of ringed seals is 249,000 animals. In 2010 the trend in numbers for this population was unknown.[3] Ringed seals are listed as a species of "least concern" by theIUCN,[1] and were considered 'not threatened' under theEndangered Species Act in 2006. Reliable estimates of the minimum population, potential biological removal, and human-caused mortality were not available in 2006. The level of annual U.S. commercial fishery-related mortality or injury was considered insignificant. The Alaska stock of ringed seals is not considered a strategic fishery stock.[13] In 2008 the USNational Marine Fisheries Service began a conservation status review under theEndangered Species Act (ESA) to determine if listing this seal under the ESA is warranted.[19]
Ringed seals reside within 35°N and theNorth Pole, and are thus known as acircumpolar based species.Climate change is projected to affect both polar regions more than anywhere else. This means a changing climate and life for all those residing in these polar regions. As for ringed seals, two potential outcomes lie ahead in this ever-changing climate.
In the past decade, the Arctic region has faced some of its highest temperatures within the instrumental record. Furthermore, within the past 2000 years, summer temperature highs have never been harsher, based onpaleo-climate reconstructions.[20] This warming is due toclimate feedback mechanisms based on sea-ice melt. As sea ice melts, it frees up more open ocean water to be further heated, thus bringing about a positive feedback. Ocean water retains more heat than sea ice; additionally thealbedo of sea ice is much higher than that of ocean water.Ringed seals require sea ice to live and reproduce. They live most of their lives alone, only grouping together into colonies when they are on sea ice to molt, mate, or rest.[21] Without access to sea ice, ringed seals are unable to sustain life, which further affectstrophic levels both above and below.Ringed seals are both predators and prey. A predator tozooplankton and fish, the ringed seal is considered a primary consumer as well as a secondary consumer. But the tertiary consumer, or top predator, in the Arctic is the polar bear, feeding mostly on seals, including the ringed seal. Yet through further exploration, the potential fates of this Arctic food web seem to be ambiguous, leading to a very important trade off of polar bear mortality and ringed seal sustenance.[22]
Most research on ringed seals is focused on their requirement of sea-ice to live and reproduce. With climate change projected to occur most dramatically at the poles, the Arctic is fated to extremely change, mainly with the melting of ice and changes in snowfall. Ferguson et al.[23] studied ringed sealrecruitment in western Hudson Bay with a focus on six environmental variables, including: snow depth, snowfall, rainfall, the temperature when pups were born,North Atlantic Oscillation (NAO) mechanisms, and lastly the spring break-up. The results of Ferguson et al. determined that decreases in snowfall had a negative effect on ringed seal recruitment, most likely from the occurrence of earlier break up of sea ice. The main process driving this break up is albedo, with less snowfall and more ocean exposed the ice melts more quickly. With seal pups being forced into the water sooner due to lack of ice, recruitment numbers dropped and resulted in a downward trend of the population. Ringed seals are not the only animals that require sea-ice in the Arctic and Sub-Arctic to thrive. Trophic levels come into play in terms of the food web and the reliance of one population on another or many others for survival. Most of this research is actually studied through simulations, since this requires future projections and interactions between many population, physical ocean, and biological mechanisms. Meier et al.[10] studied current and future projections of climate in regards to sea-ice in the Baltic Sea by means of atmosphere-ocean models. Firstly, the ringed seal relies on sea-ice for breeding and is unable to breed on land, meaning, as ice melts away in the future, breeding grounds will become much scarcer. Only one bay,Bothnia Bay in theBaltic Sea, will be able to be used by ringed seals for breeding, vastly limiting their options. Ringed seals are only able to be successful with strained conditions in areas of 90%-100% ice cover probability. (Meier et al. 2004) The changes in ice scarcity projected for the future seem to greatly hinder the ability for ringed seals to reproduce in the Baltic Sea. Hoover et al.[22] looked at multiple marine populations in theHudson Bay while factoring in both simulated current and higher harvest rates, ultimately determining that ringed seals are identified to increase in population. This is mostly due to the decrease in polar bear populations, the main predator to the ringed seal. Even with a doubling of harvest rates and under the high (A1B) climate scenario, the ringed seals were determined to thrive even more. Hoover et al. further determined that the ringed seal's large presence as a circumpolar population along with unspecialized feeding makes the ringed seal less sensitive compared with other Arctic land and marine species. One of the final general conclusions made by Hoover et al. stated that while many current harvested populations will decrease with proposed climate change, ringed seals should be considered for redirecting harvest towards their populations.
In the Hudson Bay, Canada, the body conditions of ringed seals were observed from 2003-2013. Aerial surveys showed a decline in ringed seal density, with the lowest occurrence of seals in 2013.[24] The lower ice coverage means more open water swimming for the ringed seals, which caused higher stress (cortisol) rates.[24] Low ovulation rate, low pregnancy rate, fewer pups in the Inuit harvest, and observations of sick seals was also seen over the course of the study.[24]
The ringed seal is a very important link in thefood chain, separating primary producers from primary predators. Historically the ringed seal was the most abundant of any other seals in the Arctic, yet this species has had its share of population slumps. First there was over-harvesting of the ringed seal, drastically dropping numbers from about 200,000 in 1900 to only 4,000 in the 1970s. Secondly, pollution from organochlorides due toDDT and other residues caused many Arctic marine mammals including the ringed seal to become sterile. Sterility still affects many marine mammals living in the Arctic, being a mechanism ofbioaccumulation within the Arctic food web.[10] The ringed seal is not fragile considering their past, yet climate change will have the greatest population effect on the ringed seals thus far due to anthropogenic causes.
The future of ringed seal populations in the Arctic and Sub Arctic is uncertain, but two main projections surface based around habitat and predators. The first projection focuses on the direct effects of climate change on sea-ice and the limited environment that it will provide the ringed seal with. The majority of past research has been focused around this main idea of quicker melting sea ice leading to lower ringed seal populations from lack of breeding areas. Yet what most research has not also taken into account is the quick drop in polar bear populations. As the main predator of ringed seals, the polar bears extinction in the coming years will allow for ringed seal populations to flourish. In the end, ringed seals are estimated to thrive with no polar bears present in the Arctic and Sub Arctic.[22] Although this predator factor is involved with more recent research, it does not necessarily mean this will be the outcome, considering the uncertainty in such projections. Overall, ringed seals populations will fluctuate regardless of each potential outcome and climate change is certain to affect not only the ringed seal but all Arctic and Sub Arctic animal populations.
Wikimedia Commons has media related toPusa hispida.
^abcMeier, H. E. M.; Döscher, R.; Halkka, A. (2004). "Simulated Distributions of Baltic Sea-ice in Warming Climate and Consequences for the Winter Habitat of the Baltic Ringed Seal".Ambio.33 (4):249–256.Bibcode:2004Ambio..33..249M.doi:10.1579/0044-7447-33.4.249.
M. S. Olsen, T. V. Callaghan, J. D. Reist, L. O. Reiersen,D. Dahl-Jensen, M. A. Granskog, B. Goodison, G. K. Hovelsrud, M. Johansson, R. Kallenborn, J. Key, A. Klepikov, W. Meier, J. E. Overland, T. D. Prowse, M. Sharp, W. F. Vincent, J. Walsh.
(2011). The changing arctic cryosphere and likely consequences: An overview. AMBIO: A Journal of the Human Environment, 40(sp1), 111-118. doi: 10.1007/s13280-011-0220-y.
Ringed seal - Phoca hispida. (2013). Retrieved from[1]
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